Chair frame



FIG. 1 is a perspective view of a chair frame comprising the new design;

FIG. 2 is a left view identical to mirror image of right side view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a front view thereof; and,

FIG. 5 is a top view thereof.

The broken line showing is for illustrative purposes and forms no part of the claimed design. 

The ornamental design for a chair frame, as shown and described. 